Red blood cell distribution width as a useful indicator to predict systemic vasculitis in patients with cutaneous vasculitis.

Cutaneous vasculitis can be limited to skin or a manifestation of primary systemic vasculitis. However, there are no definite markers to predict systemic involvements. Recent studies have shown that a higher red blood cell distribution width (RDW) is associated with disease activity in various disorders. We evaluated whether RDW can be used as an indicator for predicting systemic disease in patients with initial cutaneous involvements. We reviewed clinical and laboratory information of 143 patients with cutaneous vasculitis and 15 pigmented purpuric dermatosis patients seen at single academic hospital in Korea. Various parameters, including RDW, were evaluated in patients with primary cutaneous vasculitis and primary systemic vasculitis with initial cutaneous manifestations. The RDW value between cutaneous and systemic vasculitis patients was compared and RDW level was also investigated whether it can indicate systemic vasculitis in patients with cutaneous involvements. The mean age was 32.0 years, and 102 (64.6 %) patients were female. A total of 132 patients were patients with primary cutaneous vasculitis, and 11 were primary systemic vasculitis. Higher ratio of patients with high RDW was detected in systemic vasculitis group compared with cutaneous vasculitis group (36.4 vs. 7.6 %, P < 0.05). The mean RDW was significantly higher in systemic vasculitis patients (P < 0.05). RDW had the strongest association with systemic vasculitis (P < 0.05, OR 1.834). In conclusion, elevated level of RDW was significantly associated with systemic vasculitis. RDW can be used as one of the marker to predict systemic disease in patients with cutaneous vasculitis.